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6.3.1 Ecosystems (Biomass transfer (manipulation of primary productivity…
6.3.1 Ecosystems
Biomass transfer
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biomass of an organisms consists of the organic and inorganic components, excluding water; organisms is put into an oven at 80c until all the water has evaporated (dry mass)
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gross primary productivity: rate at which plants convert light energy into chemical energy through photosynthesis
net primary productivity: net amount of energy that is stored by the main energy producers of the ecosystem per unit area in unit time
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Primary succession
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deflected succession: happens when succession is stopped or interfered with; e.g. grazing or mowing the lawn
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- pioneer species e.g. sea rocket arrive at the new area; are often specialised to withstand extreme conditions e.g. salt water, lack of freshwater, unstable sand
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- mini sand dune is formed as plants die and decay; plants e.g. sea couch grass start to grow; has underground stems so sand is stabilised
- sand dunes become more stable so other plants e.g. marram grass and sea spurge grow; marram grass shoots trap blown sand and grows taller
- sand dunes and nutrients build up so other plants can colonise the sand e.g. hare's foot clover; nitrates are available
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Ecosystems
a community of animals, plants and bacteria interrelated with the physical and chemical environment; dynamic
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population: all of the organisms of one species who live in the same place at the same time and can breed together
community: all of the populations of different species who live in the same place at the same time and who can interact with each other
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cyclic changes: repeat themselves in a rhythm e.g. predator prey relationship, tides, seasons
non-cyclic changes: directional changes, tend to last longer than the lifetime of organisms in the ecosystem e.g. coastline erosion
unpredictable/erratic changes: no rhythm and no constant direction e.g. lightening, hurricanes
Recycling
role of decomposers: break down dead and waste material so energy and nutrition do not remain trapped and can be recycles; obtain a supply of energy to stay alive
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decomposition, respiration, photosynthesis
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- saprotrophs secrete enzyme onto dead and waste material
- enzymes digest material into small molecules; absorbed into the saprotrophs body
- molecules are stored or respired to release energy
Carbon cycle
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exchanges between air and water when carbon dioxide dissolves in water and reacts to form carbonic acid; also enter via weathering of limestone and chalk (hydrogen carbonate)
combustion of fossil fuels has disrupted balance of carbon dioxide between air and water; atmospheric carbon dioxide levels are higher; results in global warming
Biotic factors
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producers: plants and some photosynthetic bacteria which supply chemical energy to all other organisms
consumers: primary consumers (herbivores), secondary consumers (carnivores)
decomposers: bacteria, fungi and some animals that feed on waste or dead organisms
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Nitrogen cycle
bacteria involved: Nitrosomona, Nitrobacter
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nitrogen fixation:
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Rhizobium live in the root nodules of plants; provide plant with fixed nitrogen, and receive glucose in return
proteins such as leghaemoglobin absorb oxygen and keep conditions anaerobic; bacteria use an enzyme (nitrogen reductase) to reduce the nitrogen gas into ammonium ions to be used by host plants
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